The area of a rectangle gets reduced by 9 square units, if its length is
reduced by 5 units and the breadth is increased by 3 units. The area is
increased by 67 square units if length is increased by 3 units and breadth is
increased by 2 units. Find the perimeter of the rectangle. [CBSE 2012]
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Answer:
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3
Answer:
Perimeter of rectangle = 52 m
Step-by-step explanation:
Let length = x m
Let breadth = y m
Area = xy m²
ATQ:-
Case1:-
Length = (x-5)m
Breadth = (y+3)m
Area = (x-5) (y+3)
ATQ:- (x-5) (y+3) = xy - 9 ----(1)
Also,
Length = (x+3)
Breadth = (y+2)
Area = (x+3) (y+2)
ATQ:-
(x+3) (y+2) = xy + 67 ----(2)
Solve equation (1) and (2)
From equation 1:-
(x-5) (y+3) = xy - 9
xy + 3x - 5y - 15 = xy - 9
3x - 5y = -9 + 15
3x - 5y = 6 ------(3)
Now, solve equation 2
(x+3) (y+2) = xy + 67
xy + 2x + 3y + 6 = xy + 67
2x + 3y = 67 - 6
2x + 3y = 61 ----(4)
Multiply equation (3) with 2 and equation (4) with 3
We get,
6x - 10y = 12 ----(5)
6x + 9y = 183 ----(6)
Subtract equation (5) and (6)
6x - 10y = 12
6x + 9y = 183
- - -
___________
0x - 19y = - 171
___________
-19 y = -171
y = 9
Put y in equation 3
3x - 5y = 6
3x - 5(9) = 6
3x - 45 = 6
3x = 45+6
3x = 51
x = ⁵¹/3
x = 17
So, we get x= 17 and y = 9
Hence, length = 17 m
Breadth = 9 m
Perimeter of rectangle = 2(l+b)
= 2(17+9)m
= 2(26)m
= 52 m
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